Ancient Egypt City Aligned With Sun on King's Birthday

Both practical and beautiful, the 400-foot lighthouse at the mouth of Alexandria harbor started guiding sailors home around 250 BC. A fire made the lighthouse glow at night and a mirror reflected sun rays during the day, some say up to 35 miles away.

Credit: Photo Credit: The Pharos of Alexandria, an ancient lighthouse, is depicted in this hand-colored engraving by Martin Heemskerck.

The Egyptian city of Alexandria, home to one of the seven wonders of the ancient world, may have been built to align with the rising sun on the day of Alexander the Great's birth, a new study finds.

The Macedonian king, who commanded an empire that stretched from Greece to Egypt to the Indus River in what is now India, founded the city of Alexandria in 331 B.C. The town would later become hugely prosperous, home to Cleopatra, the magnificent Royal Library of Alexandria and the 450-foot-tall (140 meters) Lighthouse of Alexandria, one of the wonders of the ancient world. Today, more than 4 million people live in modern Alexandria.

Ancient Alexandria was planned around a main east-west thoroughfare called Canopic Road, said Giulio Magli, an archaeoastronomer at the Politecnico of Milan. A study of the ancient route reveals it is not laid out according to topography; for example, it doesn't run quite parallel to the coastline. But on the birthday of Alexander the Great, the rising sun of the fourth century rose "in almost perfect alignment with the road," Magli said.

The results, he added, could help researchers in the hunt for the elusive tomb of Alexander. Ancient texts hold that the king's body was placed in a gold casket in a gold sarcophagus, later replaced with glass. The tomb, located somewhere in Alexandria, has been lost for nearly 2,000 years. [8 Grisly Archaeological Discoveries]

Building by the stars

Magli and his colleague Luisa Ferro used computer software to simulate the sun's position in the fourth century B.C. (Because Earth's orbit isn't perfect, there is some variation in the sun's path through the sky over centuries.) Alexander the Great was born on July 20, 356 B.C. by the Julian calendar, which is slightly different than the modern, Gregorian calendar, because it does not have leap years to account for partial days in the Earth's orbit around the sun. On that day in the fourth century B.C., the researchers found, the sun rose at a spot less than half a degree off of the road's route.

"With a slight displacement of the day, the phenomenon is still enjoyable in our times," Magli told LiveScience.

A second star would have added to the effect, Magli said. The "King's Star" Regulus, which is found on the head of the lion in the constellation Leo, also rose in near-perfect alignment with Canopic Road and became visible after a period of conjunction with the sun near July 20. Earth's orbit has changed enough that this Regulus phenomenon no longer happens, Magli said.

Sun as a symbol

Architecture-by-astronomy was common in the ancient world, Magli said. The Great Pyramid of Giza, for example, is aligned with amazing precision along the compass points, which would have required the use of the stars as reference points. The Egyptians, whom Alexander conquered, had long associated the sun god Ra with their pharaohs.

"Aligning the city [of Alexandria] to the sun in the day of birth of Alexander was a way to embody in the architectural project an explicit reference to his power," Magli said. The King's Star would have only added to the mystique, he said.

The researchers reported their work online Oct. 9 in the Oxford Journal of Archaeology. They are now examining other cities founded by Alexander and later rulers to see if the solar pattern holds. The hope, Magli said, is that an understanding of Alexandria's astronomical layout will give researchers a better idea of where Alexander's tomb might be.

Stephanie Pappas is a contributing writer for Live Science. She covers the world of human and animal behavior, as well as paleontology and other science topics. Stephanie has a Bachelor of Arts in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. She has ducked under a glacier in Switzerland and poked hot lava with a stick in Hawaii. Stephanie hails from East Tennessee, the global center for salamander diversity. Follow Stephanie on Google+.